The desire to have one's hair retain a particular set or coiffure is widely held. A common methodology for accomplishing this is by applying hair setting compositions to the hair. Hair setting compositions can assist in manipulating (styling) the hair, and provide temporary benefits in holding the shape of the hair style (fixing) and maintaining the shine or appearance (grooming, restyling) of the coiffure during the day or between hair washing periods with water or shampoo, or between subsequent hair setting procedures.
Most commercial, hair setting compositions include hair setting polymers (styling or fixative), viscosity-increasing polymers, and polymer modifiers, in addition to solvents, co-solvents, and cosmetic adjuvants, such as preservatives, color, fragrance, and the like. The amount of hair setting polymer present can vary in the range of about 0.2 to about 10 weight percent, depending on the attributes desired during application and the function of the product. See, for example, Ch. 30, Harry's Cosmeticology, 8th Ed., M. J. Rieger, Ph.D. (ed.), 666–667, Chemical Publishing Co., Inc., New York, N.Y. (2000).
Various objective and subjective methods are used to measure the efficacy of a hair setting composition. One method commonly employed evaluates the resistance of the hair set to high humidity as a measure of the curl retention. In this methodology, hair tresses are curled either before or after applying the hair setting product to the hair, and the curl retention is periodically monitored during exposure to a controlled ambient room temperature and relative humidity (RH). When curl retention is measured under controlled ambient temperatures in the range of about 23 to about 27° C. and high humidity in the range of about 80–90% RH, it is commonly referred to as high humidity curl retention (HHCR). Most conventional hair setting formulations are marginally effective, typically providing an HHCR of about 70% of the initial curl for a period of not more than about 0.75 hours. Thus there is an ongoing need for an increase in the HHCR of hair setting formulations.
Hair setting compositions are also subjectively evaluated by visual and tactile sensory methods by examining, touching, combing, and brushing the hair, or instrumentally, for characteristics, such as appearance (shiny, clean, natural), feel (stiffness, tack-free, softness), curl memory (bounce, and restylability), combing ease, residue (flaking), static, smoothness, and the like. Conventional hair setting polymers also have a tendency to coat and dull the hair. Thus, there is an ongoing desire for non-dulling, hair setting polymers.
Also of importance are the aesthetic characteristics and appearance of hair setting compositions before, during, and after application to hair. Preferably, the product viscosity should be non-runny to avoid dripping during application. Product clarity is preferably substantially transparent or clear in order to obtain a “clean” product appearance. The product should be easy to spread, have a smooth texture, a non-tacky feel, and be able to dry relatively quickly on the hair.
Conventional polymeric hair styling or hair fixative polymers, well known in the art, include natural gums and resins and neutral or anionic polymers of synthetic origin. Some commercially available neutral or anionic polymers, which have been used as hair styling or fixative polymers include, for example, polyvinylpyrrolidone (PVP), polyvinylpyrrolidone/vinylacetate copolymer (PVP/VA), and acrylates/hydroxyesters acrylates copolymers (Rohm and Haas). For example, U.S. Pat. No. 4,196,190 to Gehman, et al., discloses an acrylic hair fixative resin made via emulsion polymerization techniques containing between 10 to 30 weight % of an alkyl acrylate, between 41 to 60 weight % of methyl methacrylate, between 5 to 20 weight % of hydroxyethyl methacrylate, and between 10 to 30 weight % of methacrylic acid. Acrylate/acrylamide copolymers (National Starch and BASF), ethyl and butyl esters of polyvinyl methyl ether/maleic anhydride copolymer (PVM/MA) (GANTREZ®, ISP), and a copolymer of vinylpyrrolidone/acrylic acid/lauryl methacrylate (STYLEZE™ 2000, ISP) are other examples.
One of the shortcomings of conventional hair setting resins and fixative polymers is that they generally do not provide significant thickening or contribute significant rheological modification at practical use concentrations. Consequently, conventional hair setting compositions typically require, in addition to the hair setting or fixative polymer, the addition of one or more viscosity-increasing thickener or gellant, such as a polymer, gum or resin, and other rheology modifying additives, such as emulsifiers, waxes, and the like, to achieve the desired rheological property. A few examples of synthetic and natural polymers that have been used as gellants in commercial hair fixative products include carbomer polyacrylic acid polymers, and hydrophobically-modified variations thereof, sold under the registered trademark CARBOPOL®, such as CARBOPOL® 980 polymer, CARBOPOL® 940 polymer, CARBOPOL® Ultrez 10 polymer, CARBOPOL® Ultrez 21 polymer, CARBOPOL® ETD 2020 polymer, and the like by Noveon, Inc., (Cleveland, Ohio), hydrophobically modified cellulose, xanthan gum and hydrophobically modified, alkali-swellable, emulsion polymers.
A prior art attempt to achieve a crosslinked acrylate polymer that was both a hair fixative and thickener was disclosed in U.S. Pat. No. 3,726,288 to Nowak, et al. However, the polymers disclosed were produced by an organic solvent-based polymerization process using toxic organic solvent (benzene) and, while thickening was achieved, hair fixative properties were weak (curl retention of less than 50% after 0.5 hours at 72° F. (about 22° C.) and 90% relative humidity).
Hydrophobically modified alkali-swellable and alkali-soluble emulsion polymers, conventionally referred to as HASE polymers, are associative polymers. An associative polymer contains pendant groups capable of forming non-specific “associations” with other groups in the polymer or other materials in the medium in which the polymer is present. Generally the pendant group has both hydrophobic and hydrophilic regions and the associations are generally based on hydrophobic interactions. Hydrogen bonding associations between hydrophilic groups have also been seen under some pH conditions. According to theory, such associations result in thickening by the formation of interpolymer networks above a critical polymer overlap concentration.
HASE polymers are typically polymerized as stable emulsions at low pH (pH<4.5) but become water swellable or soluble at near neutral to neutral pH (pH>5.5–7). Typical HASE polymers are vinyl addition copolymers of pH sensitive or hydrophilic monomers, hydrophobic monomers and an “associative monomer”. The associative monomer has a polymerizable end group, a hydrophilic midsection and a hydrophobic end group. An extensive review of HASE polymers is found in Gregory D. Shay, Chapter 25, “Alkali-Swellable and Alkali-Soluble Thickener Technology A Review”, Polymers in Aqueous Media—Performance Through Association, Advances in Chemistry Series 223, J. Edward Glass (ed.), ACS, pp. 457–494, Division Polymeric Materials, Washington, D.C. (1989), the relevant disclosures of which are incorporated herein by reference.
However, conventional hair setting and hair fixative polymers frequently are incompatible with the rheology modification agent or gellant resulting in loss of viscosity, lack of gel product clarity, and aggregation, coalescence, or coacervation. Consequently, hair fixative polymers suitable for use, especially in gel formulations, may be limited primarily to neutral (i.e., uncharged, nonionic) polymers, such as PVP, and PVP/VA, but these polymers are marginally effective in retaining a hair style or curl, impart a tacky, sticky feel to hair at conditions of relatively high humidity, and a raspy, harsh feel to dry hair. Additionally, the need for viscosity thickening or gellant additives increases the risk of leaving an unwanted residue or dull coating on the hair.
Another problem is that polymeric thickeners and polymeric hair fixatives, which are supplied in powder form, present difficult storage and handling problems during manufacturing processes, and often require complex or elaborate dispensing and processing equipment, thereby increasing manufacturing costs.
There is an ongoing need and desire, therefore, for a rheology modifying, hair setting polymer providing both thickening and hair fixative properties. It has now been surprisingly found that certain hydrophobically modified, associative polymers disclosed herein provide both hair setting efficacy and rheology modification to aqueous hair setting formulations.